2, 5, 10, 17, 26, 37, 50, 64

The pattern is 1 ², 2 ², 3 ², 4 ², 5 ², 6 ², 7 ². But, instead of 5 ², it is 20 which to be turned out.

Each of the numbers except 23, is perfect square.

Each of the numbers except 28, is a multiple of 3.

In each number except 427, the middle digit is the sum of other two.

Each of the numbers except 54 is multiple of 5.

Each of the numbers except 21 is an even number.

Each of the numbers except 72 is a perfect square.

In each number except 383, the product of first and third digits is the middle one.

In each number except 751, the difference of third and first digit is the middle one.

Each of the numbers except 81 is a prime number.